The present invention relates to the inspection of turbines, and particularly axial flow gas turbines in which the condition of interior regions of the turbine must be monitored or inspected at regular intervals.
In such turbines it is necessary to make regular inspections to determine if any deleterious conditions exist in the flow path of the hot gases through the turbine, such as erosion of the blades, or if any damage has been caused by foreign particles which may have entered the flow path. Such inspections may, of course, be made by partial disassembly of the turbine structure but this is an expensive and time-consuming operation which is to be avoided if possible. Satisfactory inspections can also be made by means of inspection ports which provide access to the interior of the turbine at the desired locations and permit insertion of a borescope, or other suitable instrument, for examining the condition of the turbine. Such inspection ports must, of course, be closed and sealed during operation to prevent escape of the hot pressurized gas flowing through the turbine, or the entrance of cool air or of foreign particles such as dirt. The sealing means must effectively and reliably seal the opening into the turbine and must be easily accessible from the outside of the turbine in a manner to facilitate disassembly and removal of the sealing means when an inspection is to be made. The sealing means must also be such that after the inspection is completed, it can be readily replaced and reassembled in the inspection port to again seal the access opening with a seal which effectively reproduces the original seal.